ON COLLECTING- MICROSCOPIC AND 
OTHER ORGANISMS IN ROCKS. 
The interiors of chalk flints and nodules of chert from the Green- 
sand frequently have hollows containing loose whitish or greenish 
powder. This should be collected, for it usually has small organisms 
such as Foraminifera or Sponge spicules scattered through it ; and 
they may be obtained by levigating the loose powder, or, where the 
material is silicified, by treating it with dilute acid. 
The thin shaly partings between layers and beds of limestone often 
contain microscopic organisms, and should be examined ; also the 
heaps of debris from quarries and other workings in limestone 
frequently have small fossils weathered out ; and this kind of material 
is often much more easily worked by washing than that fresh from 
the quarry. 
The surface of ploughed fields, or fields in the autumn when the 
crops have been gathered off, frequently yield fossils in those instances 
in which limestone or other rocks,. are near the surface. Often 
molluscan and other shells and many other calcareous fossils become 
silicified, and are thus rendered more durable than the limestone 
matrix ; and they remain when the rest of the rock has been dissolved. 
Thus it happens that nodules and stones picked from the surface of 
fields for the repair of roads, etc., often contain good fossils; and 
heaps of such materials by the roadsides will repay careful scrutiny. 
The materials thrown out from ditches, trenches, well-sinkings, 
and all kinds of excavations should be examined for fossils ; and a 
good pocket-lens should be used to detect microscopic Foraminifera or 
Ostracoda in decayed shales, etc. 
The outcropping edges of rock -beds in old disused quarries and in 
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